1. Field of the Invention
The present invention generally relates to a method for repairing process-related damage of a dielectric film by hydrocarbon restoration and hydrocarbon depletion using UV irradiation.
2. Description of the Related Art
Dielectric films are indispensable to increasing processing speed of semiconductor devices and lowering power consumption of the devices. The dielectric films are susceptible to damage during their manufacturing processes, thereby increasing dielectric constants and/or leakage currents. Such process-related damage includes damage caused by dry etching and plasma ashing, and washing with chemicals, and physical damage by chemical mechanical planarization (CMP), etc. In order to repair such process-related damage of the dielectric films, U.S. Pat. No. 7,851,232 and U.S. Patent Application Publication No. 2011/0159202 (U.S. Pub, '202), for example, disclose repairing damage by UV-excited reaction using a gas containing carbon. However, although damaged surfaces can be restored to a certain degree by the above methods using a hydrocarbon film (U.S. Pub. '202), restoration is insufficient depending on the degree of damage. A hydrocarbon film can restore the damaged surfaces (e.g., porous surfaces) by sealing pores, and depending on the degree of damage, by further forming a protective film (U.S. Pub. '202). However, restoration by sealing pores and forming a protective film has limited effect, and even if the duration of the above restoration is extended, such an extended process provides more carbon to the damaged surface and increases a thickness of the protective hydrocarbon layer, but does not sufficiently repair the damaged layer. For example, after the restoration by UV irradiation with a hydrocarbon gas, a dielectric constant recovery rate, R, of the restored dielectric film is about 70% at most (for example, see the Examples discussed later), wherein R=(∈1∈*)/(∈1−∈0)×100 where ∈0 is the dielectric constant of the dielectric film prior to the damage exerted thereto, ∈1 is the dielectric constant of the damaged dielectric film, and ∈* is the dielectric constant of the restored dielectric film.
Any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.